台灣為海島國家位於季風氣候區其年平均雨量約為世界平均雨量之2.5倍,而台灣地形陡峻、坡短流急,因此在降雨後容易造成坡面之土壤流失情況發生。故若能針對台灣集水區之坡地表土沖蝕且建立一套兼顧台灣地理環境特性的土壤沖蝕量評估模式,將有助於坡地防災相關工作之參考。 本研究以台灣各流域集水區之現地沖蝕釘試驗數據,進行土壤沖蝕之探討及其資料之建置,並且運用統計分析軟體之線性迴歸,建立土壤沖蝕量之評估模式,再利用各試區之降雨數據及自然環境因子資料,分析其對土壤沖蝕量之影響。 本研究以坡度、覆蓋、高程、距水系距離、表土剪力強度、土壤硬度相關參數及降雨強度為影響土壤沖蝕之因子,其相關性檢定係數皆為於低度或微弱相關。結果顯示本研究建立之線性迴歸模式所推估之土壤沖蝕量,與現地量測得到之土壤沖蝕量之總平均相對誤差約為33%,而土壤沖蝕指數之總平均相對誤差為40%。再者,研究結果顯示,在觀測期間內坡度與降雨強度若增加,則土壤沖蝕量亦有隨之增加的趨勢;若土壤硬度相關參數及剪力強度愈大,則相對沖蝕量愈小。
Taiwan is an island country and in the monsoon climate zone. Taiwan's average annual rainfall is about 2.5 times the world's average rainfall. In Taiwan, the terrain is steep, slope is short and water flow is acute. The loss of slope soil occurs frequently after the rain. Therefore, to study the soil erosions in the Taiwan catchment area and to establish a set of evaluation model of the soil erodibility are helpful to slope disaster prevention. The data of rainfall, natural environmental factors, and field erosion pins test in Taiwan watershed catchments were used to explore soil erosion and to establish a data set. The evaluation model for soil erosion was obtained using linear regression model. In this research, factors affecting soil erosion include slope, vegetation cover, elevation, distance from the water system, shear strength of soil surface, related parameters of soil hardness and rainfall intensity. The coefficient of correlation test is low. The results show that the total average relative error of the estimated soil erosions is about 33% compared with soil erosions measured in situ. The total average relative error of soil erosion index is 40%. Furthermore, if the slope and rainfall intensity increase during observation, the amount of soil erosion also increases. If the related parameter of soil hardness and the shear strength is larger, the relative erosion quantity is smaller.
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